PLANTATION, Fla. – Factor in the wind chill, and the temperature in St. Paul, Minn., sinks below zero degrees at night. Even if Alexis Nelson was back home this week, the weather outside might not matter that much.

Nelson ensured at least one more night in balmy Plantation on Friday by reaching the girls’ 16s singles final at the Metropolia Orange Bowl International Tennis Championships, taking down No. 4-seeded Lisa Ponomar of Germany, 7-5, 4-6, 6-4, at the Frank Veltri Tennis Center.

It was a match Nelson led, 4-1, in the second set before Ponomar won five straight games to push it to three. Nelson relinquished a third-set lead, as well, before buckling down and advancing to the final, where she’ll play fifth-seeded Charlotte Robillard-Millette of Canada.

Asked afterward how she managed to refocus on court and prevail, Nelson said it was mental strength. She turned 15 in August but seems to have the right state of mind to join past Orange Bowl girls’ 16s champions, such as Chris Evert and Mary Joe Fernandez, even if she lives in a state more associated with sticks and pucks than racquets and balls.

“My previous matches have all been really tough, and they’ve been close, too, so that was mentally challenging,” Nelson said. “But once you know that you’ve been mentally tested and you’ve still come out on top and been able to pull yourself back together after you lose a couple of games you think you should have won, that really boosts your confidence.

“You can’t dwell on what happened or what could have happened. You just have to focus on what’s ahead," she added. "There’s nothing you can do about the past. I’ve learned that.”

Nelson learned tennis from her father, David, who continues to coach her in St. Paul. Even as her development has progressed, they’ve stayed in Minnesota, whereas other families may have sought warmer environs more conducive to year-round, outdoor tennis training.

Around Minnesota, Nelson has had some nice competition with Ingrid Neel, who was out in the first round here, and Jessie Aney, who plays hockey this time of year. Mostly, Nelson trains at the Fred Wells Tennis & Education Center but sometimes bounces from club to club – often indoors – hitting with local pros and high school boys.

“It’s not really so much where you are as long as you go out on the court with the right mindset every day,” Nelson said. “You don’t need to be hitting in an academy to get the same effect. It’s nice to be in that environment, but you have to create that environment for yourself.”

On the court adjacent to Nelson and Ponomar, 15-year-old Sofia “Sonya” Kenin marched through to the semifinals of the girls’ 18s draw – the only American left, after No. 3 Tornado Alicia Black lost to No. 6 Ioana Ducu of Romania, 5-7, 6-3, 6-4. Kenin, of nearby Pembroke Pines, Fla., took down her second top-five seed of the tournament, beating No. 5 Marie Bouzkova of the Czech Republic, 6-2, 7-6.

“I just fight for every point, no matter what. I try to think positive, and if we would have split in sets, I would have some way found a way to win,” Kenin said. “I’m really happy. I’m playing really good here. I’m showing really good results, and hopefully I can end the year really good.”

Two American boys advanced to the 18s singles semifinals for the first time since 2008, when future University of Virginia teammates Jarmere Jenkins and Alex Domijan did. Fifteen-year-olds Stefan Kozlov and Francis Tiafoe will each play for a spot in Sunday’s final, after No. 4 Kozlov defeated No. 8 Naoki Nakagawa of Japan, 6-1, 5-7, 6-3, and No. 13 Tiafoe dispatched No. 7 Roman Safiullin of Russia, 6-4, 6-4.

Tiafoe, from College Park, Md., will meet No. 2 Johan Sebastien Tatlot of France, while Kozlov, from Pembroke Pines, will get the tournament’s top seed and the No. 1-ranked junior in the world, Germany’s Alexander Zverev.

Kozlov is 2-0 against Zverev this year. He beat the towering French Open junior finalist, 6-2, 6-0, in the second round of a USTA Pro Circuit $10,000 Futures event in Texas two months back and eliminated him in the third round of the Wimbledon Junior Championships in July, when Zverev retired in the third set.

“I don’t take it for granted,” Kozlov said. “I beat him, 0 and 2, last time, but I’m the underdog still. He’s a great player. He’s the No. 1 in the world for a reason, so I’m going to go out there as an underdog again and expect the best.”

The top-seeded boys’ 16s doubles team, Korea’s Yunseong Chung and Chan-Yeong Oh, held true to their seeding, winning the title on Friday, 6-1, 6-4, against Korea’s Soon Woo Kwon and William Genesen, from Tulsa, Okla.

Chung and Oh will play against each other on Saturday for the boys’ 16s singles title. Kwon and Genesen reached the doubles final, despite never having met one another before this tournament. They were paired together because they each needed a partner.